1. Field of the Invention
The present invention relates to image forming apparatuses having an image reading function, such as a facsimile apparatus, a copying machine, a scanner, and a digital complex machine.
2. Description of the Related Art
Conventionally, there has been a known image forming apparatus including a document feeding section of a sheet-through type and a document reading section for reading a document fed by the document feeding section. In such image forming apparatus, when foreign objects such as a spot of whiteout and dust adhere on a document reading position, such foreign object is included into image data of the read document as a black line. Therefore, a technology for preventing such inclusion of black line in image data is disclosed in Japanese Patent Unexamined Publication No. 2000-196814. According to this technology, foreign objects adhered on a document reading position are detected, and the document reading position is moved to a position where no foreign object adheres. Then, a document reading start timing is delayed in accordance with the moving distance of the document reading position.
Further, according to a technology disclosed in Japanese Patent Unexamined Publication No.2000-310820, an image of a reference plate is read out, and it is determined that a foreign object is adhered on a document reading position when a density of the read image of the reference plate is equal to or higher than a predetermined density. Then, an image reading position is set to be at a position where no foreign object adheres.
In these conventional image forming apparatuses, the document feeding section notifies the document reading section that a document is placed when the sheet sensor of the document feeding section detects the document placed on the document holding portion. Then, the document reading section notifies moving distance information indicating a moving distance of the document reading position to the document feeding section. The document feeding section delays the feed start timing of the document in accordance with the received moving distance information such that the document arrives at the document reading position when the document reading section outputs an instruction to start reading the document to the image sensor.
However, in the conventional image forming apparatuses, since various data such as moving distance information are transmitted between the document feeding section and the document reading section as described above, and both sections are serially connected, there has been a problem that loss of communication is likely to occur, and successive reading of documents cannot be performed efficiently.